Millimeter-wave, also known as mm-wave for short, is electromagnetic wave with frequencies which fall between those of microwave and light wave. In general, millimeter-wave features frequencies of 30˜300 GHz and wavelengths of 1˜10 mm. Millimeter-wave provides broadband. Due to information explosion, data streams are ever-increasing in a manner that data streams beyond 4 G (B4G) will increase 1000 times by year 2020 and 10,000 times by year 2025. In view of this, the technology about the transmission of millimeter-wave is regarded as crucial to the capability of transmitting data streams at high flow rates and thus plays an important role in the development of B4G communication technology and even 5G communication technology.
Referring to FIG. 1a, the prior art about a glass-based high-performance 60 GHZ/millimeter-wave phase array antenna is disclosed by U.S. Pat. No. 8,901,688 issued on Dec. 2, 2014. The millimeter-wave phase array antenna comprises cavities 11 disposed in a phased-array antenna (PAA) substrate 10. The cavities 11 are disposed below planar antenna elements (12, 13). Emitter traces 14 are disposed on the PAA substrate opposite the planar antenna elements (12, 13) and the emitter traces 14, the cavities 11 and the planar antenna elements (12, 13) are vertically aligned. The aforesaid structural arrangement requires precise vertical alignment of the cavities 11 and the planar antenna elements (12, 13) to the detriment of the configuration of an RFIC die 15 of a through-silicon via (TSV) 16 and the TSV 16; as a result, not only higher costs are incurred, but, however mild, an error also leads to transmission loss.
Referring to FIG. 1b, an active electronically scanned array antenna is disclosed in US2013/0321228 published on Dec. 5, 2013. The active electronically scanned array antenna comprises a body 21. Circular holes 25 defined on the body 21 are aligned with circulators 22, respectively. The body 21 is mounted on a radiator base 23 by a plurality of fastening elements, such as screws. Coaxial connectors 24 are coupled to predetermined an emission port and a receiving port of the body 21, thereby forming a radiator stick 20. The aforesaid assembly structure, however, is so complicated that imprecision of alignment, however mild, causes transmission loss.
Referring to FIG. 1c, a phased-array antenna is disclosed in US2014/0333480 published on Nov. 13, 2014. The phased-array antenna radio-frequency integrated-circuit chip apparatus 30 is disposed on a phased-antenna array base 32 and comprises planar antenna elements 31 which are arranged to form a rectangular pattern and spaced apart from each other. The aforesaid arrangement, however, renders the spacing between the antennas overly small to the detriment of the installation of an emitting/receiving module.
Referring to FIG. 1d, an antenna array is disclosed in U.S. Pat. No. 8,242,966 issued on August 14. The antenna array comprises an antenna 40. The antenna 40 comprises a first antenna unit 41, second antenna unit 42, third antenna unit 43 and fourth antenna unit 44 which are put together in a three-dimensional configuration. The aforesaid design, however, renders it difficult to mount an emitting/receiving module.
In view of the aforesaid drawbacks of the prior art, it is important to integrate antennas of a millimeter-wave array with reference to microwave integrated circuit design concepts but still achieve low signal transmission loss and meet the demand for commercialization and mass production. For instance, given a 5G communication system, antenna design requires that a beam scan comes with an allowance of +30 degrees or so. The requirement causes antenna spacing to fall within the range of 0.6λ˜0.7λ (i.e., 4.7˜5.5 mm); as a result, the small antenna spacing leads to two problems with waveguide millimeter-wave array antenna as follows: (1) the required precision of the waveguide antenna mechanism is too strict to carry out efficient production; (2 the spacing of waveguide antennas is too small to allow an external emitting/receiving module of K-connector or waveguide flange to function.